Keyshaun Mason, who had just started his freshman year at Potomac High School, died Monday morning after police say his mother's boyfriend stabbed him and his 18-year-old brother when they tried to break up an argument.

Police said Sean Crawford, 48, stabbed the brothers inside the home they shared on the 600 block of Audrey Lane in Oxon Hill, Maryland.

"My kids responded. They did what they felt was needed to see if I was safe," mother Lakisha Jenkins said Tuesday. "Keyshaun was a very caring person. He would do whatever he possibly thought he needed to do if he cared about you."

Oxon Hill Man Killed Girlfriend's Teen Son, Police Say

News4's Darcy Spencer reports on what led up to a deadly stabbing in Oxon Hill, Maryland and the arrest police made in the case.

(Published Monday, Oct. 19, 2015)

According to the charging documents, the victims tried to help Jenkins after she and Crawford argued all night and into the morning. At some point, police say Crawford grabbed a kitchen knife and barricaded himself and the Jenkins inside a bedroom.

Mason and his brother forced their way into the bedroom and tried to ask Crawford to leave. Crawford then stabbed Mason in the chest and his brother in the shoulder in front of their mother, police said.

Officers were called to the scene about 7:25 a.m. Monday. Mason was pronounced dead on the scene. His brother was treated and released and was recovering on Tuesday at his father's house.

"What we're seeing increasingly is having children who are killed. We've had four children in the last 18 months in this exact same scenario, Prince George's County State's Attorney Angela Alsobrook said.

Jenkins suggested she had thought she could help Crawford, who prosecutors say has a record for domestic crimes in Maryland and D.C.

"We have had a short-time relationship, however there are some things you feel maybe you can contribute to a person to help them in any form or fashion, and I think sometimes you never think helping someone will end up in this manner," Jenkins said.

After speaking about her son on Tuesday, the distraught mother collapsed and needed to be carried away.

Crawford, who prosecutors said has a history of domestic violence in Maryland and D.C., has been charged with first-degree murder and attempted first- and second-degree murder. He is being held without bond and faces life in prison without parole if convicted. It was not clear if he has an attorney.